The invention relates to a pump for generating pressure or negative pressure, and, more particularly to a pump comprising a pump chamber which has a high-pressure port and a low-pressure port, two rotors having at least two blades and fitted to two parallel shafts in the pump chamber that are offset to each other, a drive arranged on an end face of the rotors, and a housing cover arranged on the opposite side.
With pumps of this type, the blades of the rotors engage each other without having any contact, so that a lubricate-free operation is made possible. Hence, there are manifold fields of application for such pumps. Due to the manifold application possibilities of these pumps, an optimization with respect to the size, the weight and the production costs is aimed at.
From U.S. Pat. No. 4,057,375 there is known a positive-displacement pump comprising two blade wheels which rotate in synchronism and with opposite sense of rotation, and the blades of which, due to their meshing engagement, form distinct spaces with changeable volume during the rotary motion; in these spaces, a compressed flow medium is conveyed from the low-pressure side to the high-pressure side, the flow medium being conveyed in a direction perpendicular to the two axes.
Further, in GB 2 139 287 A there is disclosed a hydraulic pump comprising two toothed wheels being in meshing engagement, which are disposed in a chamber into the envelope of which open inlet and outlet channels.
With these known pumps, the rotors are supported on both sides, i.e. on each of the two axle ends. The pump chamber is limited on both end faces by a part of the housing cover. The suction and pressure channels open into the envelope of the pump chamber.
In EP 0 389 838 A2 there is described a rotating piston pump in the form of a roots compressor having two rotors which are arranged cantilevered on two axles being parallel to each other and which make possible the continuous conveying of various incompressible flow media. The rotors are disposed in a chamber which on the side of the gear box is limited by a flat platexe2x80x94through which the axles of the rotors are passed in a fluid-tight mannerxe2x80x94and on the side facing away from the gear box is limited by a housing cover in the envelope of which are arrangedxe2x80x94guided radially to the outsidexe2x80x94connection ports for inlet and outlet.
The invention provides a pump enabling inner compression of the medium to be delivered, the pump having a space-saving and simple structure and allowing to provide the low-pressure and high-pressure openings on the housing in an end face position.
This is achieved according to the invention in that the housing cover is configured cup-shaped and the high-pressure port as well as the low-pressure port are integrated in the housing cover, the inner wall of the housing cover delimiting the pump chamber on an end face and having two axial openings for the high-pressure and the low-pressure port and the axial openings each being adjoined by one channel which is integrated in the body of the housing cover, the axial opening for the high-pressure port, in operation of the pump, being covered by one of the rotors for a time to enable inner compression of the delivered medium.
Preferably, the axial opening for the high-pressure port is significantly smaller than the axial opening for the low-pressure port. Thus, the opening for the high-pressure port can be easily covered by for a time by one of the rotors with its claw-shaped blades, in contrast to the relatively large opening for the low-pressure port through which medium is continuously delivered into the pump chamber.